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Re: [Tigers] Subaru Master Cyl. - Do the math

To: "Stu Brennan" <stubrennan@comcast.net>, <tigers@autox.team.net>
Subject: Re: [Tigers] Subaru Master Cyl. - Do the math
From: "Teepen, Jere" <jteepen@usatoday.com>
Date: Sat, 22 Mar 2008 14:46:34 -0400
 Stu:

>From my experience a master cylinder with a .70 bore is the way to go
when not using a booster. Good pedal feel and very effective response.
Girling does make these units, and I get mine from Doug Jennings at
Tiger Auto.  This is one of the many things I learned from Doug
Jennings.

Jere



-----Original Message-----
From: tigers-bounces+jteepen=usatoday.com@autox.team.net
[mailto:tigers-bounces+jteepen=usatoday.com@autox.team.net] On Behalf Of
Stu Brennan
Sent: Saturday, March 22, 2008 8:17 AM
To: tigers@autox.team.net
Subject: [Tigers] Subaru Master Cyl. - Do the math

I think I found the Subaru master cylinder we are talking about, at
NAPA.  It's an '80, not '81.  Their data says the bore is 13/16.  OK,
calculator time



A 13/16 bore has a piston area of about.0.518 square inches.  My spare
Tiger master is a 0.875 bore, with an area of about 0.601 sq . in.  So
for the same pedal pressure, the Subaru master will produce about 16%
more pressure in the brake line than the stock master.  Sounds great,
but remember that the booster is not in service, so you loose it's
pressure amplification, which, IIRC, was much greater than the minimal
gain above.



So the math seems to indicate that there is a significant increase in
pedal pressure for the same amount of braking effect.



Now, a master with a 5/8 inch bore would have a piston area of about
0.306 sq. in., which would provide a gain of about 2 over stock, which
would come closer to the original system performance.  Does such a piece
exist?



I've driven my Tiger with the booster bypassed with the original master
cyl, and for me, it was not a pleasant experience.  Maybe if your
college sport was football, you can manage it, but I'm not quite that
muscular.



Other opinions?  Have I missed something?



Stu
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